269 research outputs found
Advanced asteroseismic modelling: breaking the degeneracy between stellar mass and initial helium abundance
Current stellar model predictions of adiabatic oscillation frequencies differ
significantly from the corresponding observed frequencies due to the
non-adiabatic and poorly understood near-surface layers of stars. However,
certain combinations of frequencies -- known as frequency ratios -- are largely
unaffected by the uncertain physical processes as they are mostly sensitive to
the stellar core. Furthermore, the seismic signature of helium ionization
provides envelope properties while being almost independent of the outermost
layers. We have developed an advanced stellar modelling approach in which we
complement frequency ratios with parameters of the helium ionization zone while
taking into account all possible correlations to put the most stringent
constraints on the stellar internal structure. We have tested the method using
the Kepler benchmark star 16 Cyg A and have investigated the potential of the
helium glitch parameters to constrain the basic stellar properties in detail.
It has been explicitly shown that the initial helium abundance and
mixing-length parameters are well constrained within our framework, reducing
systematic uncertainties on stellar mass and age arising for instance from the
well-known anti-correlation between the mass and initial helium abundance. The
modelling of six additional Kepler stars including 16 Cyg B reinforces the
above findings and also confirms that our approach is mostly independent from
model uncertainties associated with the near-surface layers. Our method is
relatively computationally expensive, however, it provides stellar masses,
radii and ages precisely in an automated manner, paving the way for analysing
numerous stars observed in the future during the ESA PLATO mission.Comment: 18 pages, 14 figures (including 5 in the appendix), 3 tables, MNRAS
in pres
Neonatal Urine Metabolic Profiling and Development of Childhood Asthma
none9Urine metabolomics case-control studies of childhood asthma have demonstrated a discriminative ability. Here, we investigated whether urine metabolic profiles from healthy neonates were associated with the development of asthma in childhood. Untargeted metabolomics by liquid chromatography-mass spectrometry was applied to urine samples collected at age 4 weeks in 171 and 161 healthy neonates born from mothers with asthma from the COPSAC2000 and COPSAC2010 cohorts, respectively, where persistent wheeze/asthma was prospectively diagnosed using a symptom-based algorithm. Univariate and multivariate analyses were applied to investigate differences in metabolic profiles between children who developed asthma and healthy children. Univariate analysis showed 63 and 87 metabolites (q-value 0.60. Database search enabled annotation of three discriminative features: a glucoronidated compound (steroid), 3-hydroxytetradecanedioic acid (fatty acid), and taurochenodeoxycholate-3-sulfate (bile acid). The urine metabolomics profiles from healthy neonates were associated with the development of childhood asthma, but further research is needed to understand underlying metabolic pathways.noneChawes, Bo L; Giordano, Giuseppe; Pirillo, Paola; Rago, Daniela; Rasmussen, Morten A; Stokholm, Jakob; Bønnelykke, Klaus; Bisgaard, Hans; Baraldi, EugenioChawes, Bo L; Giordano, Giuseppe; Pirillo, Paola; Rago, Daniela; Rasmussen, Morten A; Stokholm, Jakob; Bønnelykke, Klaus; Bisgaard, Hans; Baraldi, Eugeni
Association of bacteria and viruses with wheezy episodes in young children: prospective birth cohort study
Objective To study the association between wheezy symptoms in young children and the presence of bacteria in the airways
A Protocol for Extraction of Infective Viromes Suitable for Metagenomics Sequencing from Low Volume Fecal Samples
The human gut microbiome (GM) plays an important role in human health and diseases.
However, while substantial progress has been made in understanding the role of bacterial inhabitants
of the gut, much less is known regarding the viral component of the GM. Bacteriophages (phages)
are viruses attacking specific host bacteria and likely play important roles in shaping the GM.
Although metagenomic approaches have led to the discoveries of many new viruses, they remain
largely uncultured as their hosts have not been identified, which hampers our understanding of
their biological roles. Existing protocols for isolation of viromes generally require relatively high
input volumes and are generally more focused on extracting nucleic acids of good quality and
purity for down-stream analysis, and less on purifying viruses with infective capacity. In this study,
we report the development of an efficient protocol requiring low sample input yielding purified
viromes containing phages that are still infective, which also are of sufficient purity for genome
sequencing. We validated the method through spiking known phages followed by plaque assays,
qPCR, and metagenomic sequencing. The protocol should facilitate the process of culturing novel
viruses from the gut as well as large scale studies on gut viromes
An asteroseismic age estimate of the open cluster NGC 6866 using Kepler and Gaia
Asteroseismology of solar-like oscillations in giant stars allow the
derivation of their masses and radii. For members of open clusters this allows
an age estimate of the cluster which should be identical to the age estimate
from the colour-magnitude diagram, but independent of the uncertainties that
are present for that type of analysis. Thus, a more precise and accurate age
estimate can be obtained. We aim to measure asteroseismic properties of
oscillating giant members of the open cluster NGC 6866 and utilise these for a
cluster age estimate. Model comparisons allow constraints on the stellar
physics, and here we investigate the efficiency of convective-core overshoot
and effects of rotation during the main-sequence, which has a significant
influence on the age for these relatively massive giants. We identify six giant
members of NGC 6866 and derive asteroseismic measurements for five of them.
This constrains the convective-core overshoot and enables a more precise and
accurate age estimate than previously possible. Asteroseismology establishes
the helium-core burning evolutionary phase for the giants, which have a mean
mass of 2.8 . Their radii are significantly smaller than predicted
by current 1D stellar models unless the amount of convective-core overshoot on
the main sequence is reduced to in the
step-overshoot description. Our measurements also suggest that rotation has
affected the evolution of the stars in NGC 6866 in a way that is consistent
with 3D simulations but not with current 1D stellar models. The cluster age is
estimated to be 0.43 0.05 Gyr, significantly younger and more precise
than most previous estimates. We derive a precise cluster age while
constraining convective-core overshooting and effects of rotation in the
models. We uncover potential biases for automated age estimates of helium-core
burning stars.Comment: Accepted on 21/08/2023 for publication in Section 7. Stellar
structure and evolution of Astronomy & Astrophysics. 20 Pages, 11 Figures +
appendi
Phylogenomic insights to the origin and spread of phocine distemper virus in European harbour seals in 1988 and 2002
The study was supported by the Villum Foundation, the Danish Ministry of the Environment, the Volkswagen Foundation (Az.: 89911) and the BONUS programme BaltHealth, which has received funding from BONUS (Art. 185), funded jointly by the EU, Innovation Fund Denmark (grants 6180-00001B and 6180-00002B), Forschungszentrum Jülich GmbH, German Federal Ministry of Education and Research (grant FKZ 03F0767A), Academy of Finland (grant 311966) and Swedish Foundation for Strategic Environmental Research (MISTRA).The 1988 and 2002 phocine distemper virus (PDV) outbreaks in European harbour seals Phoca vitulina are among the largest mass mortality events recorded in marine mammals. Despite its large impact on harbour seal population numbers, and 3 decades of studies, many questions regarding the spread and temporal origin of PDV remain unanswered. Here, we sequenced and analysed 7123 bp of the PDV genome, including the coding and non-coding regions of the entire P, M, F and H genes in tissues from 44 harbour seals to shed new light on the origin and spread of PDV in 1988 and 2002. The phylogenetic analyses trace the origin of the PDV strain causing the 1988 outbreak to between June 1987 and April 1988, while the origin of the strain causing the 2002 outbreak can be traced back to between July 2001 and April 2002. The analyses further point to several independent introductions of PDV in 1988, possibly linked to a southward mass immigration of harp seals in the winter and spring of 1987−1988. The vector for the 2002 outbreak is unknown, but the epidemiological analyses suggest the subsequent spread of PDV from the epicentre in the Kattegat, Denmark, to haul-out sites in the North Sea through several independent introductions.PostprintPeer reviewe
Influence of errors in job codes on job exposure matrix-based exposure assessment in the register-based occupational cohort DOC*X
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